function obj(oid){
	this.oid = oid;
	this.layer = null;
	this.sons = { };
	this.attributes = { };
}
obj.prototype.addSon = function(new_son){
	this.sons[new_son.oid] = new_son;	
};
obj.prototype.getChildren = function(){
	return this.sons;
};
obj.prototype.hasChildren = function(){
	var s = this.sons;
	var i = 0;
	for (var x in s)	{ i++; }
	if (i != 0) { return true; }
	else { return false; }
}

obj.prototype.addAttr = function(new_attr){
	this.attributes[new_attr.oid] = new_attr;	
};
obj.prototype.getAttr = function(){
	return this.attributes;
};
obj.prototype.hasAttr = function(){
	var s = this.attributes;
	var i = 0;
	for (var x in s)	{ i++; }
	if (i != 0) { return true; }
	else { return false; }
}
